Objectives. To investigate whether serum levels of tumour necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) are related to mortality and severity of disease in patients admitted to the Emergency Department (ED). Design. Prospective cohort study. Setting. Emergency Department of a tertiary university hospital. Subjects. A total of 140 patients admitted to the ED, representing common acute medical diseases, such as stroke, obstructive lung disease, heart failure, myocardial infarction, angina pectoris, infectious diseases and acute abdominal disorders. Main outcome measures. APACHE II score at admission, hospital mortality and length of stay in hospital (LOS). Results. A moderate rise in cytokine levels (IL-6; 50-300 ng L-1, TNF-alpha; 10-70 ng L-1) was found in all diagnosis-groups, with the most pronounced elevation seen in patients with acute abdominal disorders (up to 6900 ng L-1). IL-6 on arrival to the ED was significantly correlated to the APACHE II score (r = 0.48, P < 0.0001), LOS (r = 0.36, P < 0.0001) and was elevated in nonsurvivors (n = 9) compared to those who did survive. TNF-alpha on arrival showed a significant correlation to LOS (r = 0.36, P < 0.0001) and APACHE II (r = 0.41, P < 0.0001), but was not associated to later mortality. Conclusions. Serum levels of proinflammatory cytokines collected at admission to the ED were related to the severity of disease and hospital mortality.